Absorption refrigeration



/ I INVENTOR A; ATTORNEY W. G. KOGEL ABSORPTION REFRIGERATION Filed June7 1945 Jan. 16, 1951 Patented Jan. 16, I951 2,538,011 ABSORPTIONREFRIGERATION Wilhelm Georg Kiigel, Stockholm, Sweden, as-

signor to Aktiebolaget Elektrolux, Stockholm, Sweden, a corporation ofSweden Application June 7, 1945, Serial No. 598,125 In Sweden June 10,1944 3 Claims. 1

This invention relates to absorption refrigerating apparatus employing athermosiphon pump, and has for its object to provide an improvement toeliminate the danger of the pump pipe becoming clogged which sometimesoccurs in hermetically closed absorption refrigerating apparatusincluding apparatus of the type containing a corrosion protectivesubstance, such as an alkali chromate, for example, dissolved in theabsorption solution,

It is already known to provide a liquid circulating pump for absorptionrefrigerating apparatus in the form of a pipe having a small internaldiameter, so that vapor formed in such pipe due to heating will producea thermosiphon efl'ect and thereby eifect circulation of absorptionsolution between an absorber and boiler of the apparatus. In order toobtain suflicient pumping action, a relatively small length of thepump-pipe is generally heat-conductively connected to the heatabsorbingelement of the apparatus, usually a flue. The intense heating of thenarrow pipe greatly increases the danger of the narrow passage thereinbecoming clogged by precipitation of solid matter when overheating ofthe pumppipe should occur, in view of the fact that it contains only avery small quantity of liquid.

On the other hand, it is known to employ, in place of a heat-operatedpart of a pump-pipe, an unheated dome into which the riser pipe of thepump depends with its lower open end extending downwardly into theliquid within the dome. By producing a small excess of pressure in thevapor space of the dome, slugs of liquid are repeatedly segregated bythe vapor and pass upwardly through the pipe by vapor lift action. Suchsocalled bell-pumps are, however, not suitable in every type ofabsorption refrigerating apparatus and in certain cases operate lesssatisfactorily than thermosiphon-pumps of the type first mentioned.

In accordance with the present invention, an improvement is provided inwhich all of the advantages associated with bell pumps are obtainedwhile the disadvantages of such pumps are substantially eliminated. Thisis accomplished by heated part 01' the pump pipe and such liquid, due tothe thermosiphon effect, passes upwardly through the pump-pipe andthereby eiiects circulation of liquid between the absorber of theapparatus and its boiler.

The invention, together with the objects and advantages thereof, will bemore fully understood from the following description and accompanyingdrawing illustrating different arrangements for practicing theinvention, and in which Fig. l more or less diagrammatically illustratesan absorption liquid circuit of absorption refrigerating apparatusincluding a generator embodying the invention which is shown in section.

Fig. 2 is a view in elevation of a form of generator which is differentfrom that of Fig. 1 and to which the invention has been applied;

Fig. 3 is a fragmentary sectional view of the bottom part of a generatorlike that shown in Fig. 1 illustrating another modification of theinvention; and.

Fig. 4 is a fragmentary view, partly in section, of a generatorgenerally like that shown in Fig 2 illustrating details of a furthermodification.

In Fig. 1, l0 designates a heat-absorbing eleconnected to the flue 10along a common genproviding a pump in which at least the lower parteratrix. The upper part or extension I 2 of the pipe II is connected tothe condenser of the apparatus, not shown.

To the lower part of the boiler pipe III is connected a liquidcirculating pump I4 and it of the apparatus for lifting absorptionsolution to the higher level in a stand-pipe I3. The heatabsorbing partll of the pump is formed of piping having a relatively large internaldiameter, and preferably from one and one-half to two times the diameterof the riser pipe IS, so that free relative movement of vapor and liquidcan take place in such heat-absorbing part, for example. The lower endof the pipe section It is connected by a short conduit I 5 to the boilerI i, while the upper end thereof is connected to the riser pipe IQ ofthe pump which has an internal diameter of such which such lower part isof greater internal diameter than the riser pipe of the pump. While theoperation of the pump or the invention is not fully understood, it isbelieved that a mixture of vapor and liquid is formed in the largerlower to thermally separate to a certain extent the narrow pipes I5 andI6 from the flue l0, whereby heat will be supplied to the pumpprincipally by heat transfer from the flue to the larger pipe section M.The solution pumped into the standa M and I6. After flowing through theouter passage of the liquid heat exchanger, solution weak in refrigerantpasses through a conduit i8 to the absorber 1 of the apparatus. In awell known manner inert gas rich in refrigerant enters an absorbervessel 2! through a conduit 8 and inert gas weak in refrigerant passesfrom the upper end of absorber I through a conduit 9.

The boiler H is supplied with absorption solution rich in refrigerantfrom the inner passage of the heat exchanger which is formed of pipingand connected at its upper end at l9 to boiler pipe H, such connectingpoint being located at a level with or above the highest point of theliquid heat exchanger. A conduit 20 connects the opposite end of theinner passage of the liquid exchanger to an absorber vessel 2| of theapparatus, partly shown. The boiler unit and the heat exchanger areembedded in a body of heatinsulation 22.

Fig. 3 illustrates another embodiment of the invention which isgenerally like Fig. 1 and differs therefrom in that the pump-chamber I4is formed of one leg of the boiler pipe II whose lower end is bent intoU-form. In this way the narrow passage provided by the conduit i (Fig.1), as well as the welded joint between such conduit and the pumpchamber M, respectively, are avoided.

In Fig. 2 the invention is embodied in a type of generator unit in whichthe chamber of the boiler is formed by the flue Ill and a tubular member25 which is concentrically disposed about and spaced from the flue.communicates through a conduit 26 with the condenser of the apparatus,not shown. From the boiler solution weak in refrigerant passes through aconduit 21 and the outer passage of the liquid heat exchanger I! to theabsorber. In this embodiment the liquid heat exchanger ll is arrangedoutside the heat insulation of the generator unit, not shown, and in awell known manner may be embedded in a body of insulating material. Theinternal pipe Q9 of the liquid heat exchanger is connected to 'a pipe 28which is welded to the flue l0 and forms the pump chamber. The upper endof the pipe 28 i connected to the riser-pipe 29 of the pump. This latterpipe 29 is connected to the upper part of the tubular member 25 of theboiler.

It has proved particularly advantageous when constructing thermosiphonpumps of the invention to reduce as much as possible the number 4 ofwelded joints in the pump or parts immediately associated therewith.Such welded joints, in individual instances, sometimes tend tocontribute to clogging taking place in the narrow pump passage. Theembodiment of Fig. 3 illustrates one manner of reducing the number ofwelded joints at the pump, and Fig. 4 shows another manner ofaccomplishing this result.

In the embodiment of Fig. 4, in which the reference numerals correspondto those in Fig. 2, the liquid heat exchanger is formed and connected tothe boiler and the absorber vessel, respectively, so that the solutionweak in refrigerant flows from the boiler 25 through the internal pipei9 thereof to the absorber, while the external pipe The chamber of theboiler thereof leads rich solution from the absorber vessel directly tothe riser pipe 28 of the thermosiphon-pump.

The outer tubular member or piping III or the liquid heat exchanger isbent upwardly at one end, such bent portion 31 being welded to the fluein along a common generatrix, that is, on a line substantially parallelto the longitudinal axis of the flue. The upwardly bent end portion IIof the outer piping of the exchanger forms the chamber of the pump.Through the opening at the top of this chamber extend the internal pipeI9 of the liquid heat exchanger as well as the riser pipe 29, the upperedge of the pipe portion 3| being flattened and welded about both thepipes 29 and i9. This arrangement for flowing the rich solution directlyto the riser pipe of the pump through the outer jacket or pipe of theliquid heat exchanger, and for flowing weak solution from the boilerthrough the internal pipe of the liquid heat exchanger may, of course,also be applied to boilers like those shown in Figs. 1 and 3, forexample.

In view of the foregoing, it will now be understood that the inventionis not limited to the embodiments diagrammatically shown but may bevaried in several ways within the scope of the basic spirit of theinvention. The chamber of the pump may thus be formed in different ways,as will be evident from comparing the diflerent embodiments illustrated.

In most cases it is desirable to reduce to a minimum the number ofwelded joints between the pump chamber and other parts of the apparatus.Therefore, is is advantageous for the chamber of the pump to be formedof a special part of a pipe of sufliciently large dimensions which isemployed as another part of the apparatus, as exemplified by theembodiments of Figs. 3 and 4. If the dimension of such pipe, havingregard to the function of the other part of the apparatus, cannot bechosen suiiiciently large, the portion of the pipe to be utilized as thechamber of the pump may be enlarged with the aid of suitable tools.

In certain cases it may be advantageous, in order to insure normalpumping, to separate the chamber of the pump from the solution inletpipe by providin a constriction in the pipe, like the constrictionformed by the conduit IS in Fig. 1, for example, whereby a certainresistance against back flow of liquid will be created.

Considering the comparatively short longitudinal extent of the pumpchamber, difficulties may in certain cases arise in obtaining asufficient thermal contact-surface with the heat-absorbing element ofthe apparatus. In such cases this contact-surface may be enlarged bysuitably deforming both the flue pipe and pump pipe to increase theheat-conductive relation therebetween.

It has already been mentioned that the operation of the pump is notfully understood. The pump of the invention appears, however, to difiermaterially from conventional thermosiphonpumps, on the one hand, whichare formed of only a single narrow pipe, and also from socalledbell-pumps, on the other hand. It is possible in each instance to choosesuch dimensions for the pump chamber that the volume of liquid liftedper unit of time through the pump, by suitable choice of dimension ofthe heat conductive relation between the pump chamber and the flue,remains essentially constant and independent of the magnitude of theheating eifect supplied to the flue when this exceeds a certain minimumvalue. Stated another way, by providing an upright pipe having a largerlower part and a narrower upper part and by joining at least the largerlower part to the flue in heat transfer relation therewith on a linesubstantially parallel to the longitudinal axis of the flue, it ispossible to obtain normal lifting of absorption liquid through the pumppipe over a wide range of heat input to the flue.

'Ihermosiphon-pumps of the type heretofore provided show a very sharplydefined maximum value of pumping action since it rises rapidly to amaximum value, and, with continued increase in heat input, drops almostas rapidly. This is especially troublesome, particularly in largeapparatus, in that it jeopardizes the normal lifting of absorptionliquid by the pump. Under such conditions the pump may be depleted ofliquid and produce an operating condition tending to promote corrosion.In the pump of the invention, however, no such sharply defined maximumvalue of pumping action occurs but the pumping action remainssubstantially constant and normal lifting of liquid is maintained over awide range of heat input to the flue and at least up to power values ofa magnitude of 400 watts and, in certain cases, up to 500 watts.

I claim:

1. In an absorption refrigeration system. an upright heating tube, acircuit for absorption liquid including aflrst upright boiler pipeconnected to receive liquid at a region removed from the lower endthereof, a second upright pipe and a pump comprising a third uprightvapor lift pipe connected to receive liquid in a lower part thereof fromthe lower end of said first pipe and deliver liquid from a narrowerupper part thereof to the upper part of said third pipe, at least one ofsaid first and second pipes and at least the lower part of said thirdpipe being 40 Joined to the exterior surface of said heating tube inheat transfer relation therewith on lines substantially parallel to thelongitudinal axis of said heating tube, the lower part of said thirdpipe allowing free relative movement of vapor and liquid therein andhaving a larger cross-sectional area than the narrower upper partthereof through which liquid is raised by vapor lift action and heatingmeans for heating at least one of said first and second pipes to expelvapor from absorption liquid therein and for heating said third vaporlift pipe to raise liquid therein only by vapor formed in liquid afterit passes into the lower larger part of said third pipe from said firstpipe, said heating means comprising a single source of heat for heatingthe inner surface of said heating tube in a lengthwise direction of thelatter along a zone including the region the lower larger part of saidthird pipe is in heat transfer relation with said tube.

2. In an absorption refrigeration system, an upright heating flue, acircuit for absorption liquid including a first upright boiler pipe anda pump comprising a second upright pipe arranged to receive liquid in alarger lower portion thereof from a lower part of said boiler pipe anddeliver liquid from an upper narrower portion thereof, said boiler pipeand at least the' lower larger portion of said second pipe being joinedto said heating flue in heat transfer relation therewith on linessubstantially parallel to the longitudinal axis of said heating flue,the lower end of said first pipe being bent back upon itself andconstituting and serving as the lower larger portion of said secondpipe,

3. In an absorption refrigeration system, an upright heating flue, acircuit for absorption liquid including a first upright boiler pipe anda pump comprising a second upright pipe adapted to receive liquid in alower larger portion thereof and deliver liquid from :an upper narrower'portion thereof, said boiler pipe and 'at least the lower largerportion of said second pipe being Joined to said heating flue in heattransfer relation therewith on lines substantially parallel to thelongitudinal axis of said flue, and a' conduit of smallercross-sectional area than the larger lower portion of said second pipeconnecting the latter and a lower part of said first pipe.

WILHELM GEORG KbGEL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Great Britain May 3, 1943

